I had an idea how to mod those sp's to trigger some other gear(hardware&software) like having a midi-out.
The downside on this is that you have to use a computer(these devil machines!)
It needs some skills for soldering and I would have tried it but I don't have any sp for the moment...(this is the part where you make me a present!)
The concept is simple:
Get a usb-joystick(they are really cheap),break it,change the wiring of the buttons to the pads,download a freeware midi utility for using the joystick as notes and you have a nice diy controller...so
Don't throw away your broken sp's
PS.I want 50% of the modders profit....

that's a cool idea!
how it works to use usb joystick as notes?

http://www.otk.it/mjoy/
freeware

I used to wonder if there's a header coming off the interface before it goes into the logic stuff... there are 2 boards in the 404 right?

If there is then should be able to read the data from the entire control interface, would need a bit more complex software interpreter but could be interesting to make the 404 into a controller then build an advanced-404 in reaktor or max or something